1. Field of the Invention
The present invention relates to an image forming apparatus, an image forming system, and a method of producing a printed product.
2. Description of the Related Art
Technologies have so far been known that allow higher quality printing results to be obtained by performing pretreatment on a sheet to be printed immediately before printing in an image forming apparatus. For example, plasma treatment can be performed as the pretreatment on a surface of the sheet. An image forming system that performs the pretreatment includes, for example, a pretreatment apparatus and an image forming apparatus; a sheet fed from a sheet feeding unit is fed to the pretreatment apparatus and is pretreated, and the sheet output from the pretreatment apparatus after the pretreatment is completed is fed to the image forming apparatus.
The sheet to be printed is often provided as a cut sheet that is cut in advance in a predetermined size, such as A4 size or B5 size, or as continuous sheet. One of type of a continuous sheet that has a roll form among types of the continuous sheet is specially called a rolled sheet.
The pretreatment apparatus and the image forming apparatus often differ from each other in conveying speed and conveying timing of the sheet. Hence, technologies have already been known that allow the difference in conveying speed and conveying timing of the sheet to be absorbed by providing a sheet buffer area that temporarily stores the sheet between the pretreatment apparatus and the image forming apparatus. When the rolled sheet is used as the sheet to be printed, the sheet buffer area temporarily stores the sheet, for example, by bending the sheet so as to absorb the difference between the conveying speeds in the pretreatment apparatus and the image forming apparatus.
Japanese Patent Application Laid-open No. 2012-081608 discloses a printer that includes a corona treatment apparatus that performs surface treatment on a printing medium, an inkjet printer that performs printing on the printing medium with the surface treated by the corona treatment apparatus, and a buffer unit that is provided between the corona treatment apparatus and the inkjet printer and temporarily stores the printing medium by bending it.
In the configuration in which the sheet after being pretreated is bent in the sheet buffer area and conveyed to the image forming apparatus, the pretreated sheet can be stopped being conveyed while being stored in the sheet buffer area due to, for example, turning off of the power supply of the apparatus. In this case, the sheet pretreated and stored in the sheet buffer area is left in the sheet buffer area without being fed to the image forming apparatus until the next printing operation is started.
The effect of the surface treatment by the pretreatment onto the sheet decreases with time. The decrease of the surface treatment effect causes a problem that, when the sheet left in the sheet buffer area is fed to the image forming apparatus and an image is formed on the sheet, the quality of the printed image is degraded.
In view of the above, there is a need to obtain an appropriate effect of the surface treatment in the configuration including the sheet buffer after the surface treatment and before the image formation onto the sheet.